1. Field of the Invention
The present invention relates to a radio apparatus, and in particular to a radio apparatus including no less than two housings connected to each other.
2. Description of the Related Art
Portable radio apparatus configured to have no less than two housings which are connected so as to be opened and closed to each other, such as mobile phones, are widely used these days. Such a radio apparatus may be used for voice communication while the housings are opened to each other. The radio apparatus may be used for transmitting and receiving radio waves for data communication, watching television programs and so forth while the housings are closed to each other.
If the housings are closed to each other, an antenna provided in one of the housings and a printed circuit board contained in another one of the housings may be arranged to be close to each other, thus causing impedance of the antenna to be lowered and radiation efficiency of the antenna to be degraded.
Such a problem shall be carefully considered particularly for radio apparatus having a built-in antenna in one of the housings for downsizing, down-weighting and design reasons.
Apart from the above, electromagnetic shielding by using magnetic material has been studied to be applied to radio apparatus like mobile phones so as to suppress unnecessary radiation of radio waves toward human bodies, as disclosed in Japanese Patent Publications of Unexamined Applications (Kokai), No. 2004-304440 and No. 2005-124043.
More specifically, JP 2004-304440 discloses a radio apparatus configured to have a key sheet forming an input device (a key operation portion) and to have radio wave absorbing material formed by a keypad base or keypad buttons for which magnetic material has been mixed. It is mentioned that the above configuration of the radio apparatus may contribute to suppressing radio wave radiation toward human bodies.
Meanwhile, JP 2005-124043 discloses a radio apparatus configured to be provided with a dump sheet containing magnetic material around a display. It is mentioned that the dump sheet containing magnetic material may concentrate magnetic fields of radio frequencies around the display so as to absorb the magnetic fields, thus contributing to suppressing radio wave radiation toward human bodies.
The radio apparatus disclosed in JP 2004-304440 is configured to have the key operation portion near a spot (often called a hotspot) of a housing of the radio apparatus to which radio frequency currents are concentrated so as to control the radio frequency currents.
If the radio apparatus disclosed in JP 2004-304440 is configured to have no less than two housings which are connected so as to be opened and closed to each other, radiation efficiency of an antenna of the radio apparatus may hardly be improved while the two housings are closed depending on a design of the radio apparatus, particularly an arrangement of the key operation portion and a positional relationship with the antenna.
The radio apparatus disclosed in JP 2005-124043 may be considered a same as the radio apparatus disclosed in JP 2004-304440 except that a portion formed by containing magnetic material is arranged not in the key operation portion but around the display.
Thus, if the radio apparatus disclosed in JP 2005-124043 is configured to have no less than two housings which are connected so as to be opened and closed to each other, radiation efficiency of an antenna of the radio apparatus may hardly be improved while the two housings are closed depending on a design of the radio apparatus, particularly an arrangement of the display and a positional relationship with the antenna.